Acyclovir 800 mg Tablet, 100-count — NDC 23155-228-01 (Billing 23155-0228-01)
This is a package of 100 tablets of Acyclovir 800 mg Tablet from Heritage Pharmaceuticals Inc. d/b/a Avet Pharmaceuticals Inc., marketed since Aug 2013 and currently FDA-listed; retail pharmacies pay about $0.1940 per tablet (NADAC). It is the main listing for this product, which comes in 2 package sizes.
Identity & classification
Regulatory identifiers FDA, NLM and CMS codes for this package
Drug-database identifiers Medi-Span GPI and First Databank GCN / HICL / AHFS classification
- GSN (GCN sequence number): 015979
- GCN: 13721
- HICL (First Databank): 004183
- AHFS class code: 08:18.32.00
- RxCUI (RxNorm): 197311
Where does this data come from?
- FDA openFDA NDC Directory · synced Oct 1, 2026
- FDA label on DailyMed · label index refreshed Oct 1, 2026
- RxNorm (NLM RxNav) · catalog refreshed Oct 1, 2026
- Medi-Span GPI (licensed)
- First Databank (licensed) · refreshed Oct 1, 2026
RxNorm drug class
This medicine belongs to the Herpesvirus Nucleoside Analog DNA Polymerase Inhibitor class.
Where does this data come from?
- RxClass (NLM) · catalog refreshed Oct 1, 2026
Clinical
- Acyclovir treats infections caused by herpes-family viruses. Oral forms treat shingles, genital herpes and chickenpox. Creams, ointments, the eye ointment, the buccal tablet and th...
- As early as possible. For cold sores, that means at the first tingling, itching or burning. For genital herpes recurrences, start at the first sign of an outbreak. Early treatment...
- The most common ones are headache, nausea and belly pain. Some people also get vomiting, dizziness or fatigue. These are usually manageable, but tell me if they bother you.
- Call right away for confusion, hallucinations, seizures or unusual drowsiness. Also call if you urinate much less than usual, which can signal kidney trouble. Any allergic reaction...
Patient education
Supplement & herbal interactions
Some supplements/herbs that may interact with Acyclovir — tap one for details:
Where does this data come from?
- MedlinePlus (NLM) · refreshed Oct 1, 2026
- FDA label on DailyMed · label index refreshed Oct 1, 2026
Ask a licensed pharmacist directly — free, answered by our team.
Pricing
A drug doesn't have one price. Each row is a different public payment system, and none is what you'd pay at the counter — that depends on your insurance. The ⓘ on each row explains what it measures.
| Price system | Per ea | Per package |
|---|---|---|
| Retail pharmacies payNADAC · weekly | $0.194 | $19.40 / 100 tablets |
| Medicaid paysCMS SDUD · 12 mo | $0.3675 | $36.75 / 100 tablets |
| Medicare drug plans payPart D · Q2 2026 | $0.1848 | $18.48 / 100 tablets |
Where does this data come from?
- CMS NADAC weekly file · file of Sep 30, 2026
- CMS ASP pricing files · refreshed Sep 20, 2026
- CMS Medicaid State Drug Utilization Data · through Q1 2026
- CMS Part D plan pricing files · refreshed Sep 24, 2026
- VA National Acquisition Center price file
Packaging — all sizes for this product
| Package NDC | Description | Per unit | Per pack | Marketing start | Marketing end | Status |
|---|---|---|---|---|---|---|
| 23155-0228-01 You're viewing this Main listing | 100 TABLET in 1 BOTTLE | $0.1940 / ea | $19.40 | 2013-08-08 | — | Active |
| 23155-0228-05 23155-228-05 | 500 TABLET in 1 BOTTLE | $0.1940 / ea | $97.02 | 2013-08-08 | — | Active |
You're viewing the smallest of 2 pack sizes for this product.
This pack has the lowest per-ea cost of the 2 priced pack sizes ($0.1940 NADAC).
In Medicaid, this is the most-dispensed pack of this product — about 100% of fills over the last four reported quarters. See all packs ↓
Pack size FAQ
What quantity is in this package?
How does this package differ from NDC 23155-0228-05?
What NDC number is used to bill for this package of Acyclovir 800 mg Tablet?
Prices are the latest CMS NADAC pharmacy acquisition cost per NDC; per-pack figures are per-unit × pack quantity, shown only when the pack is denominated in the same measure NADAC prices.
Therapeutic equivalents
| Product | Labeler | Pack | NADAC/unit | TE | Status | Price vs. this |
|---|---|---|---|---|---|---|
| Acyclovir 800 mg 69117-0019-01 | YILING | 100 tablets | $0.190 | AB | FDA listed | save 2% |
| Acyclovir 800 mgthis 23155-0228-01 | Heritage | 100 tablets | $0.194 | AB | Availability likely | — |
| Acyclovir 800 mg 31722-0778-01 | Camber | 100 tablets | $0.194 | AB | Availability likely | — |
| Acyclovir 800 mg 50268-0062-15 | AvPAK | 50 tablets | $0.194 | AB | Availability likely | — |
| Acyclovir 800 mg 59651-0966-01 | Aurobindo | 100 tablets | $0.194 | AB | Availability likely | — |
| acyclovir 800 mg 60505-5307-01 | Apotex | 100 tablets | $0.194 | AB | Availability likely | — |
| Acyclovir 800 mg 60687-0867-01 | American | 100 tablets | $0.194 | AB | Availability likely | — |
| Acyclovir 800 mg 61442-0113-01 | Carlsbad | 100 tablets | $0.194 | AB | Availability likely | — |
| Acyclovir 800 mg 62135-0019-50 | Chartwell | 50 tablets | $0.194 | AB | Availability likely | — |
| acyclovir 800 mg 68382-0792-01 | Zydus | 100 tablets | $0.194 | AB | Availability likely | — |
| Acyclovir 800 mg 69367-0138-01 | Westminster | 100 tablets | $0.194 | AB | Availability likely | — |
| Acyclovir 800 mg 69452-0291-20 | Bionpharma | 100 tablets | $0.194 | AB | Availability likely | — |
| Acyclovir 800 mg 43063-0589-10 | PD-Rx | 10 tablets | — | AB | FDA listed | — |
| Acyclovir 800 mg 50090-6335-00 | A-S | 35 tablets | — | AB | FDA listed | — |
| Acyclovir 800 mg 50090-6578-00 | A-S | 35 tablets | — | AB | FDA listed | — |
| Acyclovir 800 mg 51407-0146-01 | Golden | 100 tablets | — | AB | FDA listed | — |
| Acyclovir 800 mg 51655-0679-35 | Northwind | 35 tablets | — | AB | FDA listed | — |
| Acyclovir 800 mg 54348-0624-10 | PharmPak, | 10 tablets | — | AB | FDA listed | — |
| Acyclovir 800 mg 60760-0778-35 | St. | 35 tablets | — | AB | FDA listed | — |
| acyclovir 800 mg 63187-0192-30 | Proficient | 30 tablets | — | AB | FDA listed | — |
| acyclovir 800 mg 63187-0366-30 | Proficient | 30 tablets | — | AB | FDA listed | — |
| Acyclovir 800 mg 63187-0574-06 | Proficient | 6 tablets | — | AB | FDA listed | — |
| Acyclovir 800 mg 63629-1678-00 | Bryant | 500 tablets | — | AB | FDA listed | — |
| acyclovir 800 mg 63629-9174-01 | Bryant | 50 tablets | — | AB | FDA listed | — |
| acyclovir 800 mg 65841-0803-01 | Zydus | 100 tablets | — | AB | FDA listed | — |
| acyclovir 800 mg 66267-0399-15 | NuCare | 15 tablets | — | AB | FDA listed | — |
| acyclovir 800 mg 67046-1487-03 | Coupler | 30 tablets | — | AB | FDA listed | — |
| Acyclovir 800 mg 67296-2254-04 | Redpharm | 35 tablets | — | AB | FDA listed | — |
| Acyclovir 800 mg 68071-2408-01 | NuCare | 21 tablets | — | AB | FDA listed | — |
| Acyclovir 800 mg 68071-3222-00 | NuCare | 50 tablets | — | AB | FDA listed | — |
| acyclovir 800 mg 68071-5100-03 | NuCare | 30 tablets | — | AB | FDA listed | — |
| Acyclovir 800 mg 68788-7575-02 | Preferred | 21 tablets | — | AB | FDA listed | — |
| acyclovir 800 mg 70518-1614-00 | REMEDYREPACK | 30 tablets | — | AB | FDA listed | — |
| Acyclovir 800 mg 70518-2518-00 | REMEDYREPACK | 30 tablets | — | AB | Discontinued | — |
| Acyclovir 800 mg 70518-4186-00 | REMEDYREPACK | 10 tablets | — | AB | FDA listed | — |
| Acyclovir 800 mg 70518-4450-00 | REMEDYREPACK | 30 tablets | — | AB | FDA listed | — |
| Acyclovir 800 mg 71205-0053-30 | Proficient | 30 tablets | — | AB | FDA listed | — |
| Acyclovir 800 mg 71205-0388-30 | Proficient | 30 tablets | — | AB | FDA listed | — |
| Acyclovir 800 mg 71209-0006-05 | Cadila | 100 tablets | — | AB | FDA listed | — |
| Acyclovir 800 mg 71335-0695-00 | Bryant | 500 tablets | — | AB | Discontinued | — |
| Acyclovir 800 mg 71335-1222-00 | Bryant | 500 tablets | — | AB | FDA listed | — |
| acyclovir 800 mg 71335-1381-00 | Bryant | 500 tablets | — | AB | FDA listed | — |
| Acyclovir 800 mg 71335-2555-00 | Bryant | 500 tablets | — | AB | FDA listed | — |
| Acyclovir 800 mg 71335-9721-00 | Bryant | 500 tablets | — | AB | FDA listed | — |
| acyclovir 800 mg 72162-1724-00 | Bryant | 40 tablets | — | AB | FDA listed | — |
| Acyclovir 800 mg 72241-0027-05 | Modavar | 100 tablets | — | AB | FDA listed | — |
| Acyclovir 800 mg 75834-0123-01 | Nivagen | 100 tablets | — | AB | Discontinued | — |
| Acyclovir 800 mg 76483-0042-00 | SQUARE | 30 tablets | — | AB | FDA listed | — |
| Acyclovir 800 mg 82804-0012-30 | Proficient | 30 tablets | — | AB | FDA listed | — |
| acyclovir 800 mg 82868-0107-35 | Northwind | 35 tablets | — | AB | FDA listed | — |
Where does this data come from?
- FDA openFDA NDC Directory · synced Oct 1, 2026
- FDA Orange Book · refreshed Sep 3, 2026
- CMS NADAC weekly file · file of Sep 30, 2026
Availability & generic status
This product is an FDA-approved generic. Other versions of the same drug are listed under Therapeutic equivalents, least expensive first.
Where does this data come from?
- FDA Orange Book · refreshed Sep 3, 2026
What it looks like
Where does this data come from?
- FDA label on DailyMed · label index refreshed Oct 1, 2026
Inactive Ingredients / Excipients
Inactive ingredients, also called excipients, are components of the drug product other than the active ingredient. They may include fillers, dyes, coatings, preservatives, flavors, or other formulation ingredients.
Where does this data come from?
IACT rows and label-wide narrative are kept separate; availability and product-level specificity depend on the submitted label.- FDA label on DailyMed · label index refreshed Oct 1, 2026
- FDA openFDA NDC Directory · synced Oct 1, 2026
Inactive ingredient FAQ
Are inactive ingredients the same for every manufacturer?
Why might an inactive ingredient be missing?
Can inactive ingredients matter?
Manufacturer & labeler
Where does this data come from?
- FDA openFDA NDC Directory · synced Oct 1, 2026
- Drugs@FDA
Full prescribing information FDA SPL
🎯 Indications and Usage ▾
INDICATIONS AND USAGE Herpes Zoster Infections: Acyclovir tablets are indicated for the acute treatment of herpes zoster (shingles). Genital Herpes: Acyclovir tablets are indicated for the treatment of initial episodes and the management of recurrent episodes of genital herpes. Chickenpox: Acyclovir tablets are indicated for the treatment of chickenpox (varicella).
⏱️ Dosage and Administration ▾
DOSAGE AND ADMINISTRATION Acute Treatment of Herpes Zoster: 800 mg every 4 hours orally, 5 times daily for 7 to 10 days. Genital Herpes: Treatment of Initial Genital Herpes : 200 mg every 4 hours, 5 times daily for 10 days. Chronic Suppressive Therapy for Recurrent Disease: 400 mg 2 times daily for up to 12 months, followed by re-evaluation.
Alternative regimens have included doses ranging from 200 mg 3 times daily to 200 mg 5 times daily. The frequency and severity of episodes of untreated genital herpes may change over time. After 1 year of therapy, the frequency and severity of the patient's genital herpes infection should be re-evaluated to assess the need for continuation of therapy with acyclovir.
Intermittent Therapy : 200 mg every 4 hours, 5 times daily for 5 days. Therapy should be initiated at the earliest sign or symptom (prodrome) of recurrence. Treatment of Chickenpox: Children (2 years of age and older): 20 mg/kg per dose orally 4 times daily (80 mg/kg/day) for 5 days.
Children over 40 kg should receive the adult dose for chickenpox. Adults and Children over 40 kg: 800 mg 4 times daily for 5 days. Intravenous acyclovir is indicated for the treatment of varicella-zoster infections in immunocompromised patients.
When therapy is indicated, it should be initiated at the earliest sign or symptom of chickenpox. There is no information about the efficacy of therapy initiated more than 24 hours after onset of signs and symptoms. Patients With Acute or Chronic Renal Impairment: In patients with renal impairment, the dose of acyclovir tablets should be modified as shown in Table 3.
Table 3. Dosage Modification for Renal Impairment Normal Dosage Regimen Creatinine Clearance (mL/min/1.73 m 2 ) Adjusted Dosage Regimen Dose (mg) Dosing Interval 200 mg every 4 hours >10 0 to 10 200 200 every 4 hours, 5x daily every 12 hours 400 mg every 12 hours >10 0 to 10 400 200 every 12 hours every 12 hours 800 mg every 4 hours >25 10 to 25 0 to 10 800 800 800 every 4 hours, 5x daily every 8 hours every 12 hours Hemodialysis: For patients who require hemodialysis, the mean plasma half-life of acyclovir during hemodialysis is approximately 5 hours.
This results in a 60% decrease in plasma concentrations following a 6-hour dialysis period. Therefore, the patient's dosing schedule should be adjusted so that an additional dose is administered after each dialysis. Peritoneal Dialysis: No supplemental dose appears to be necessary after adjustment of the dosing interval.
Bioequivalence of Dosage Forms: Acyclovir suspension was shown to be bioequivalent to acyclovir capsules (n = 20) and 1 acyclovir 800-mg tablet was shown to be bioequivalent to 4 acyclovir 200-mg capsules (n = 24).
⛔ Contraindications ▾
CONTRAINDICATIONS Acyclovir is contraindicated in patients who have had a demonstrated clinically significant hypersensitivity reaction [e.g., anaphylaxis, severe cutaneous adverse reactions (SCARs)] to acyclovir, valacyclovir, or any component of the formulation (see WARNINGS and ADVERSE REACTIONS ).
⚠️ Warnings ▾
WARNINGS Acyclovir tablets are intended for oral ingestion only. Renal failure, in some cases resulting in death, has been observed with acyclovir therapy (see ADVERSE REACTIONS : Observed During Clinical Practice and OVERDOSAGE ). Thrombotic thrombocytopenic purpura/hemolytic uremic syndrome (TTP/HUS), which has resulted in death, has occurred in immunocompromised patients receiving acyclovir therapy.
Severe cutaneous adverse reactions (SCARs), including acute generalized exanthematous pustulosis (AGEP), drug reaction with eosinophilia and systemic symptoms (DRESS), Stevens- Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), and erythema multiforme (EM) have been reported with acyclovir (see CONTRAINDICATIONS and ADVERSE REACTIONS ). Discontinue acyclovir immediately if a painful rash with mucosal involvement or a progressive severe rash develops. Closely monitor clinical status and initiate appropriate therapy.
Acyclovir is contraindicated in patients who have developed SCARs with the use of acyclovir or valacyclovir, or any component of the formulation (see CONTRAINDICATIONS and ADVERSE REACTIONS ).
🤒 Adverse Reactions ▾
ADVERSE REACTIONS Herpes Simplex: Short-Term Administration: The most frequent adverse events reported during clinical trials of treatment of genital herpes with acyclovir 200 mg administered orally 5 timesdaily every 4 hours for 10 days were nausea and/or vomiting in 8 of 298 patient treatments (2.7%). Nausea and/or vomiting occurred in 2 of 287 (0.7%) patients who received placebo. Long-Term Administration: The most frequent adverse events reported in a clinical trial for the prevention of recurrences with continuous administration of 400 mg (two 200-mg capsules) 2 times daily for 1 year in 586 patients treated with acyclovir were nausea (4.8%) and diarrhea (2.4%).
The 589 control patients receiving intermittent treatment of recurrences with acyclovir for 1 year reported diarrhea (2.7%), nausea (2.4%), and headache (2.2%). Herpes Zoster: The most frequent adverse event reported during 3 clinical trials of treatment of herpes zoster (shingles) with 800 mg of oral acyclovir 5 times daily for 7 to 10 days in 323 patients was malaise (11.5%). The 323 placebo recipients reported malaise (11.1%).
Chickenpox: The most frequent adverse event reported during 3 clinical trials of treatment of chickenpox with oral acyclovir at doses of 10 to 20 mg/kg 4 times daily for 5 to 7 days or 800 mg 4 times daily for 5 days in 495 patients was diarrhea (3.2%). The 498 patients receiving placebo reported diarrhea (2.2%). Observed During Clinical Practice: In addition to adverse events reported from clinical trials, the following events have been identified during post-approval use of acyclovir.
Because they are reported voluntarily from a population of unknown size, estimates of frequency cannot be made. These events have been chosen for inclusion due to either their seriousness, frequency of reporting, potential causal connection to acyclovir, or a combination of these factors. General: Anaphylaxis, angioedema, fever, headache, pain, peripheral edema.
Nervous: Aggressive behavior, agitation, ataxia, coma, confusion, decreased consciousness, delirium, dizziness, dysarthria, encephalopathy, hallucinations, paresthesia, psychosis, seizure, somnolence, tremors. These symptoms may be marked, particularly in older adults or in patients with renal impairment (see PRECAUTIONS ). Digestive: Diarrhea, gastrointestinal distress, nausea.
Hematologic and Lymphatic: Anemia, leukocytoclastic vasculitis, leukopenia, lymphadenopathy, thrombocytopenia. Hepatobiliary Tract and Pancreas: Elevated liver function tests, hepatitis, hyperbilirubinemia, jaundice. Musculoskeletal: Myalgia.
Skin and Subcutaneous Tissue Disorders: Stevens-Johnson Syndrome (SJS), toxic epidermal necrolysis (TEN), acute generalized exanthematous pustulosis (AGEP), and drug reaction with eosinophilia and systemic symptoms (DRESS), erythema multiforme (EM), rashes including photosensitivity, alopecia, pruritus, urticaria (see CONTRAINDICATIONS and WARNINGS ). Special Senses: Visual abnormalities. Urogenital: Renal failure, renal pain (may be associated with renal failure), elevated blood urea nitrogen, elevated creatinine, hematuria (see WARNINGS ).
To report SUSPECTED ADVERSE REACTIONS, contact Avet Pharmaceuticals Inc. at 1-866-901-DRUG (3784) or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch.
🆘 Overdosage ▾
OVERDOSAGE Overdoses involving ingestion of up to 100 capsules (20 g) have been reported. Adverse events that have been reported in association with overdosage include agitation, coma, seizures, and lethargy. Precipitation of acyclovir in renal tubules may occur when the solubility (2.5 mg/mL) is exceeded in the intratubular fluid.
Overdosage has been reported following bolus injections or inappropriately high doses and in patients whose fluid and electrolyte balance were not properly monitored. This has resulted in elevated BUN and serum creatinine and subsequent renal failure. In the event of acute renal failure and anuria, the patient may benefit from hemodialysis until renal function is restored (see DOSAGE AND ADMINISTRATION) .
🧬 Clinical Pharmacology ▾
CLINICAL PHARMACOLOGY Pharmacokinetics: The pharmacokinetics of acyclovir after oral administration have been evaluated in healthy volunteers and in immunocompromised patients with herpes simplex or varicella-zoster virus infection. Acyclovir pharmacokinetic parameters are summarized in Table 1. Table 1.
Acyclovir Pharmacokinetic Characteristics (Range) *Bioavailability decreases with increasing dose. Parameter Range Plasma protein binding 9% to 33% Plasma elimination half-life 2.5 to 3.3 hr Average oral bioavailability 10% to 20%* In one multiple-dose, crossover study in healthy subjects (n = 23), it was shown that increases in plasma acyclovir concentrations were less than dose proportional with increasing dose, as shown in Table 2. The decrease in bioavailability is a function of the dose and not the dosage form.
Table 2. Acyclovir Peak and Trough Concentrations at Steady State Parameter 200 mg 400 mg 800 mg C SS max 0.83 mcg/mL 1.21 mcg/mL 1.61 mcg/mL C SS trough 0.46 mcg/mL 0.63 mcg/mL 0.83 mcg/mL There was no effect of food on the absorption of acyclovir (n = 6); therefore, acyclovir tablets may be administered with or without food. The only known urinary metabolite is 9-[(carboxymethoxy)methyl]guanine.
Special Populations: Adults With Impaired Renal Function: The half-life and total body clearance of acyclovir are dependent on renal function. A dosage adjustment is recommended for patients with reduced renal function (see DOSAGE AND ADMINISTRATION ). Geriatrics: Acyclovir plasma concentrations are higher in geriatric patients compared with younger adults, in part due to age-related changes in renal function.
Dosage reduction may be required in geriatric patients with underlying renal impairment (see PRECAUTIONS : Geriatric Use). Pediatrics: In general, the pharmacokinetics of acyclovir in pediatric patients is similar to that of adults. Mean half-life after oral doses of 300 mg/m 2 and 600 mg/m 2 in pediatric patients aged 7 months to 7 years was 2.6 hours (range 1.59 to 3.74 hours).
Drug Interactions: Coadministration of probenecid with intravenous acyclovir has been shown to increase the mean acyclovir half-life and the area under the concentration-time curve. Urinary excretion and renal clearance were correspondingly reduced. Clinical Trials: Initial Genital Herpes: Double-blind, placebo-controlled studies have demonstrated that orally administered acyclovir significantly reduced the duration of acute infection and duration of lesion healing.
The duration of pain and new lesion formation was decreased in some patient groups. Recurrent Genital Herpes: Double-blind, placebo-controlled studies in patients with frequent recurrences (6 or more episodes per year) have shown that orally administered acyclovir given daily for 4 months to 10 years prevented or reduced the frequency and/or severity of recurrences in greater than 95% of patients. In a study of patients who received acyclovir 400 mg twice daily for 3 years, 45%, 52%, and 63% of patients remained free of recurrences in the first, second, and third years, respectively.
Serial analyses of the 3-month recurrence rates for the patients showed that 71% to 87% were recurrence free in each quarter. Herpes Zoster Infections: In a double-blind, placebo-controlled study of immunocompetent patients with localized cutaneous zoster infection, acyclovir (800 mg 5 times daily for 10 days) shortened the times to lesion scabbing, healing, and complete cessation of pain, and reduced the duration of viral shedding and the duration of new lesion formation. In a similar double-blind, placebo-controlled study, acyclovir (800 mg 5 times daily for 7 days) shortened the times to complete lesion scabbing, healing, and cessation of pain; reduced the duration of new lesion formation; and reduced the prevalence of localized zoster-associated neurologic symptoms (paresthesia, dysesthesia, or hyperesthesia).
Treatment was begun within 72 hours of rash onset and was most effective if started wi… [Excerpted — this section continues on DailyMed.]
📦 How Supplied / Storage and Handling ▾
HOW SUPPLIED Acyclovir Tablets, USP are available as: 400 mg Bottles of 100 NDC 23155- 227-01 Bottles of 500 NDC 23155- 227-05 Each round tablet is white to off-white and debossed with HP 227 on one side and plain on the other side. Store at 20° to 25°C (68° to 77°F) [See USP Controlled Room Temperature] and protect from light and moisture. 800 mg Bottles of 100 NDC 23155- 228-01 Bottles of 500 NDC 23155- 228-05 Each oval tablet is white to off-white and debossed with HP 228 on one side and plain on the other side.
Store at 20° to 25°C (68° to 77°F) [See USP Controlled Room Temperature] and protect from light and moisture. Distributed by: Avet Pharmaceuticals Inc. East Brunswick, NJ 08816 1.866.901.DRUG (3784) Revised: 07/2026 Logo
📋 Description ▾
DESCRIPTION Acyclovir tablets, USP is a formulation for oral administration. Each tablet for oral administration contains 400 mg or 800 mg of acyclovir, USP. In addition each tablet contains the following inactive ingredients, magnesium stearate, microcrystalline cellulose, povidone, silicon dioxide and sodium starch glycolate.
Acyclovir, USP is a white, crystalline powder with the molecular formula C 8 H 11 N 5 O 3 and a molecular weight of 225. The maximum solubility in water at 37°C is 2.5 mg/mL. The pka's of acyclovir, USP are 2.27 and 9.25.
The chemical name of acyclovir, USP is 2-amino-1,9-dihydro-9-[(2-hydroxyethoxy)methyl]-6 H -purin-6-one; it has the following structural formula: VIROLOGY Mechanism of Antiviral Action: Acyclovir is a synthetic purine nucleoside analogue with in vitro and in vivo inhibitory activity against herpes simplex virus types 1 (HSV-1), 2 (HSV-2), and varicella-zoster virus (VZV). The inhibitory activity of acyclovir is highly selective due to its affinity for the enzyme thymidine kinase (TK) encoded by HSV and VZV. This viral enzyme converts acyclovir into acyclovir monophosphate, a nucleotide analogue.
The monophosphate is further converted into diphosphate by cellular guanylate kinase and into triphosphate by a number of cellular enzymes. In vitro , acyclovir triphosphate stops replication of herpes viral DNA. This is accomplished in 3 ways: 1) competitive inhibition of viral DNA polymerase, 2) incorporation into and termination of the growing viral DNA chain, and 3) inactivation of the viral DNA polymerase.
The greater antiviral activity of acyclovir against HSV compared with VZV is due to its more efficient phosphorylation by the viral TK. Antiviral Activities: The quantitative relationship between the in vitro susceptibility of herpes viruses to antivirals and the clinical response to therapy has not been established in humans, and virus sensitivity testing has not been standardized. Sensitivity testing results, expressed as the concentration of drug required to inhibit by 50% the growth of virus in cell culture (IC 50 ), vary greatly depending upon a number of factors.
Using plaque-reduction assays, the IC 50 against herpes simplex virus isolates ranges from 0.02 to 13.5 mcg/mL for HSV-1 and from 0.01 to 9.9 mcg/mL for HSV-2. The IC 50 for acyclovir against most laboratory strains and clinical isolates of VZV ranges from 0.12 to 10.8 mcg/mL. Acyclovir also demonstrates activity against the Oka vaccine strain of VZV with a mean IC 50 of 1.35 mcg/mL.
Drug Resistance: Resistance of HSV and VZV to acyclovir can result from qualitative and quantitative changes in the viral TK and/or DNA polymerase. Clinical isolates of HSV and VZV with reduced susceptibility to acyclovir have been recovered from immunocompromised patients, especially with advanced HIV infection. While most of the acyclovir-resistant mutants isolated thus far from immunocompromised patients have been found to be TK-deficient mutants, other mutants involving the viral TK gene (TK partial and TK altered) and DNA polymerase have been isolated.
TK-negative mutants may cause severe disease in infants and immunocompromised adults. The possibility of viral resistance to acyclovir should be considered in patients who show poor clinical response during therapy. structure
⚠️ Precautions ▾
PRECAUTIONS Dosage adjustment is recommended when administering acyclovir to patients with renal impairment (see DOSAGE AND ADMINISTRATION ). Caution should also be exercised when administering acyclovir to patients receiving potentially nephrotoxic agents since this may increase the risk of renal dysfunction and/or the risk of reversible central nervous system symptoms such as those that have been reported in patients treated with intravenous acyclovir. Adequate hydration should be maintained.
Information for Patients: Patients are instructed to consult with their physician if they experience severe or troublesome adverse reactions, they become pregnant or intend to become pregnant, they intend to breastfeed while taking orally administered acyclovir, or they have any other questions. Patients should be advised to maintain adequate hydration. Herpes Zoster: There are no data on treatment initiated more than 72 hours after onset of the zoster rash.
Patients should be advised to initiate treatment as soon as possible after a diagnosis of herpes zoster. Genital Herpes Infections: Patients should be informed that acyclovir is not a cure for genital herpes. There are no data evaluating whether acyclovir will prevent transmission of infection to others.
Because genital herpes is a sexually transmitted disease, patients should avoid contact with lesions or intercourse when lesions and/or symptoms are present to avoid infecting partners. Genital herpes can also be transmitted in the absence of symptoms through asymptomatic viral shedding. If medical management of a genital herpes recurrence is indicated, patients should be advised to initiate therapy at the first sign or symptom of an episode.
Chickenpox: Chickenpox in otherwise healthy children is usually a self-limited disease of mild to moderate severity. Adolescents and adults tend to have more severe disease. Treatment was initiated within 24 hours of the typical chickenpox rash in the controlled studies, and there is no information regarding the effects of treatment begun later in the disease course.
Severe Cutaneous Adverse Reactions: Inform patients that severe skin reactions including acute generalized exanthematous pustulosis (AGEP), drug reaction with eosinophilia and systemic symptoms (DRESS), Stevens-Johnson syndrome (SJS), toxic epidermal necrolysis (TEN), and erythema multiforme (EM) have been reported with acyclovir. Advise patients to immediately contact their healthcare provider if they develop a rash. Instruct patients to immediately stop taking acyclovir and seek medical attention if a painful rash with mucosal involvement develops (see CONTRAINDICATIONS and WARNINGS ).
Drug Interactions: See CLINICAL PHARMACOLOGY : Pharmacokinetics. Carcinogenesis, Mutagenesis, Impairment of Fertility: The data presented below include references to peak steady-state plasma acyclovir concentrations observed in humans treated with 800 mg given orally 5 times a day (dosing appropriate for treatment of herpes zoster) or 200 mg given orally 5 times a day (dosing appropriate for treatment of genital herpes). Plasma drug concentrations in animal studies are expressed as multiples of human exposure to acyclovir at the higher and lower dosing schedules (see CLINICAL PHARMACOLOGY : Pharmacokinetics).
Acyclovir was tested in lifetime bioassays in rats and mice at single daily doses of up to 450 mg/kg administered by gavage. There was no statistically significant difference in the incidence of tumors between treated and control animals, nor did acyclovir shorten the latency of tumors. Maximum plasma concentrations were 3 to 6 times human levels in the mouse bioassay and 1 to 2 times human levels in the rat bioassay.
Acyclovir was tested in 16 in vitro and in vivo genetic toxicity assays. Acyclovir was positive in 5 of the assays. Acyclovir did not impair fertility or reproduction in mice (450 mg/kg/day, p.o.) or in rats (25 mg/kg/day, s.c.).
In the mouse study, plasma levels were 9 to 18 tim… [Excerpted — this section continues on DailyMed.]
📄 Package Label / Principal Display Panel ▾
PACKAGE LABEL.PRINCIPAL DISPLAY PANEL NDC 23155-227-01 Acyclovir Tablets, USP 400 mg 100 Tablets Rx only NDC 23155-228-01 Acyclovir Tablets, USP 800 mg 100 Tablets Rx only 400 mg 800 mg